This invention relates to a chuck for holding work on a machine tool such as a lathe, and more specifically to such a work-holding chuck of the type having gripping jaws that are operated by a wedging action.
A wedge-operated jaw chuck of the class under consideration comprises a plurality of, normally three, gripping jaws mounted on an annular jaw carrier for sliding motion in its radial direction, and a plunger mounted in the jaw carrier for sliding motion in its axial direction to cause the radial motion of the gripping jaws by a wedging action. As heretofore constructed, each gripping jaw has its inner end portion formed into a wedge of T-shaped cross section, for sliding engagement in one of undercut wedge grooves in the plunger.
When the chuck of this familiar design is mounted on the main spindle of a lathe, for example, for holding work to be machined, the gripping jaws inevitably undergo centrifugal displacement in the radially outward direction with an increase in the speed of rotation of the spindle. The gripping force of the jaws lessens gradually, until at last the work becomes unmachinable. This drawback of the prior art will be illustrated and later explained in more detail.
One conventional attempt to overcome the above problem dictates the use of counterweights to compensate for, or take advantage of, the centrifugal forces of the gripping jaws, as disclosed in Japanese Patent Publication No. 48-15994. Although finding some acceptance in the machining industry, this known approach is nevertheless unsatisfactory in view of the complexity of configuration resulting from the use of the counterweights.